"This still leaves New Zealand in the major league, more closely linked to core countries like the U.S., U.K. and Germany than European periphery countries or emerging markets," he said. "While these are volatile times, we expect global investors to be able to put this news in context and continue to support the NZ government bond market."
S&P credit analyst Kyran Curry wasn't immediately available for comment.
Fitch's statement said the nation's high level of external debt "is an outlier among rated peers - a key vulnerability that is likely to persist as the current account deficit is projected to widen again."
Fitch's move "is a clear reminder of the ongoing vulnerabilities the NZ economy faces," said Philip Borkin, economist at Goldman Sachs & Partners New Zealand. Borkin is forecasting the current account deficit will widen to 5.5 per cent of GDP, from the 3.7 per cent rate in the second quarter.
Fitch also cited high household indebtedness and eroding public finance as contributing factors. While New Zealand household debt was on par with other AAA rated countries like the U.S., U.K. and Australia, little progress had been made in clawing this back.
Westpac chief economist Dominick Stephens said the rating downgrade will theoretically lift the cost of funds in the New Zealand economy and for the government.
"Typically you would expect to see higher government bond rates, further widening of corporate funding spreads, a lower NZ dollar and lower short-term swap rates potentially combined with higher long-term swap rates, leading to a steeper yield curve," Stephens said in a note today.
Even excluding the downgrade, the prospect of higher borrowing costs as a result of heightened financial market volatility "reinforces our view that the Reserve Bank remains firmly in wait and see mode for now," he said.